I've got a Light and Motion Vis 500 that has a low power "be seen" mode that is sort of like this... I think of it as a sinusoidal change in brightness. It goes through 7 cycles of medium to dim brightness, with a couple of quick strobes of "bright". I guess that strobe is to get people's attention, and then the varying brightness just keeps their attention? I've seen motorcycles with a similar change in brightness. At first I thought that it was just a loose headlight mount, but then I read about a circuit that would create this effect. Personally, I liked it.. it got my attention but wasn't annoying.

Steve in Peoria